One of two legal challenges to Ohio’s voting procedures could end up before the Supreme Court in the next few weeks, creating the possibility of an eleventh-hour decision affecting the nearly 8 million voters in the crucial swing state.

President Barack Obama’s re-election campaign has until Friday evening to respond to a request by Ohio Secretary of State Jon Husted (R) that the Supreme Court stay a lower court’s ruling blocking changes in the state’s early voting rules that would allow only military voters to cast ballots during the three days before Election Day.

The same federal appellate court that made that ruling is considering another case related to provisional ballots. The Service Employees International Union challenged the state’s refusal to count ballots cast in the wrong precinct as a result of poll worker error. The U.S. Court of Appeals for the Sixth Circuit is expected to weigh in on that case within the next week, and the decision could lead to another high court appeal.

There is a great deal at stake in Ohio for Obama and Republican presidential nominee Mitt Romney, both of whom are focusing on the perennial battleground state as the race narrows to just a handful of states still in play.

Romney made appearances in Ohio this week in Cuyahoga Falls, Mount Vernon, Delaware and Sidney, with more stops scheduled on Friday and Saturday. Obama was at Ohio State University on Tuesday, where he reminded students that it was the last day to register to vote and encouraged them to take advantage of early voting now under way.

Ohio’s importance is not lost on election law experts. University of California, Irvine, law professor Rick Hasen has predicted that if the Supreme Court takes up a voting case before the elections, it will be one of the two from the hotly contested Midwestern state.

In both lawsuits, liberal groups have based their challenges in part on the high court’s decision in Bush v. Gore that ended the Florida recount in the 2000 presidential election.

“I think the court would rather not have to decide anything related to the election if it can avoid it. But once these cases come, then the court has to deal with them. They raise some difficult legal questions as well as some sensitive political ones,” Hasen said. “The court may well get through another election without having to tell us what Bush v. Gore means, but it’s a very real possibility now, in a way that it wasn’t before these cases were on their way to the court.”

The dispute over Ohio’s early voting rules began last summer when Gov. John Kasich (R) signed a measure passed by the Republican-controlled legislature that ended early voting on the Friday before Election Day. After legislative maneuvering and an attempt to repeal that law by referendum, the state was left with conflicting statutes. One ends the early voting period on Friday, while another allows members of the military to continue voting until Election Day.

Husted stepped in to mitigate the confusion. He issued a directive to the state’s 88 counties that interpreted state law as setting a deadline of 6 p.m. Friday for nonmilitary voters but allowing county election boards to decide whether to remain open over the weekend before Election Day to accept in-person ballots from military and overseas voters.

The Obama campaign sued the state, arguing that it is unconstitutional to treat military and nonmilitary voters differently. A federal trial court agreed and in August stopped the changes in Ohio’s early voting window from taking effect. The Sixth Circuit last week concurred, paving the way for Ohio’s appeal that the Supreme Court lift the prohibition on changing the rules until the state can present its case.

In the provisional ballot case, the SEIU complained that the Ohio Supreme Court “adopted the most strict possible interpretation” of a statute “requiring the rejection of all wrong-precinct provisional ballots without exception, even where the County Board of Election knows that poll worker error led to the voter being provided with the wrong ballot.”

Ohioans cast 200,000 provisional ballots in the 2008 elections, and 40,000 were tossed out, according to the union’s complaint. The state increasingly uses polling locations that serve voters from more than one precinct.

A federal trial court judge ordered Ohio officials to count ballots cast in the wrong precinct unless specific criteria are met. The state asked the Sixth Circuit to review that decision, and the appellate court heard oral arguments last week. A decision is expected shortly.

Hasen said that in the decade since Bush v. Gore “scholars have been puzzling” over a passage in the high court’s ruling that is relevant to both Ohio cases.

“Having once granted the right to vote on equal terms, the State may not, by later arbitrary and disparate treatment, value one person’s right to vote over that of another,” the court’s majority wrote in its rationale for ending the Florida recount.

“Both of these cases raise the question of when you can treat similarly situated voters differently. In the early-voting case, the question is the distinction between military and nonmilitary voters. In the provisional ballot case, it’s voters who did nothing wrong who happen to encounter an incompetent poll worker and voters who did not.”

Either case would provide an opportunity for the Supreme Court to further explain its thinking in Bush v. Gore, Hasen said.